390 Dr. Gladstone on the Periods and Colours 



Colours of train. — Many meteors in their flight leave a train 

 behind them, which seems generally to be a faint luminosity, the 

 colour of which observers have not usually noted. M. Coulvier 

 Gravier finds the trains usually of the same colour as the meteor 

 itself, but he mentions several cases of red trains left by meteors 

 that became bluish as they approached the horizon. The con- 

 verse of this has been observed both in China and England, 

 namely a red star leaving a bluish vapour. Greenish trains are 

 also not uncommon in the Paris catalogue. Red sparks pro- 

 ceeding from green meteors are recorded as seen both in England 

 and in India, and the Chinese speak on one occasion of a score 

 of little red stars jumping from a globe of fire. Where a meteor 

 breaks up into smaller pieces, these not unfrequently present a 

 diflferent colour to the primary : thus an orange-red ball observed 

 by Mr. Lowe, July 4, 1851, gave out many small separate balls 

 which were bright blue, becoming purple; and the little balls 

 shot from the meteor of November 13, 1803, are described as 

 tinged with orange, yellow, and purple*. Yellow fragments 

 have also been observed fi-om a blue meteor; and the splendid 

 vari-coloured fire-ball which flew across the north of England on 

 April 27, 1851, left a train of yellow light. 



The colour of the train sometimes changes ; thus M. Coulvier 

 Gravier relates instances of trains that became greenish after 

 having been bluish or reddish, or both reddish and bluish, and 

 another instance of a clear yellow train becoming deep red. 



It not unfrequently happens that a meteor is followed a few 

 seconds afterwards by a smaller one pursuing the same path. I 

 and others have observed these to be of the same colour, but 

 they do not appear to be invariably so. 



Radiance different from ajjparent colour. — In descriptions of 

 fire-balls, it not unfrequently happens that the narrator describes 

 the luminous body as of one colour, while it casts a light of a 

 difi'erent colour on surrounding objects. Instances might be 

 quoted from the Chinese records, the most remarkable perhaps 

 being that " a blue star spread a reddish glare which lighted the 

 earth." Thus, too, in our own country a lady describes a bril- 

 liant meteor that, passing over Hampstead, " broke into an in- 

 tensely radiant cloud," which threw on the walls of the houses 

 a light brighter than that of the moon, but of a blue tint, though 

 " there was no blue light in the cloud itself." The explanation 

 of this apparent paradox will be given below. 



Sources of error. — In discussing these reputed facts, certain 

 illusions to which observers are subject must be taken into ac- 

 count. Thus there is at the very outset the difiiculty that dif- 

 ferent observers often call the same colour by different names. This 

 * Phil. Mag. First Series, vol. xvii. p. 2/9. 



